Lovato, who has struggled with addiction, is reportedly in rehab after being hospitalized for an apparent overdose.

De La Garza started off her note by writing about what Lovato’s birthday

could’ve been like had the star not made it.

“Today could have been one of the worst days of my life, but instead i get to spend it thanking God, the incredible doctors, demi’s team, and everyone across the world who offered their support — without all of these people i wouldn’t have my big sister anymore,” De La Garza captioned a photo of the two when they were younger.

“I’ve been thinking about how i wish that everyone could see the silly little things that she does, like how her nostrils move when she says certain words and when she brushes my hair behind my ear when i’m trying to sleep, because those are the things i’m thankful for today,” she added.